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Many factors influence the structure of natural assemblages. Species interaction and environmental factors may generate deterministic patterns, whereas dispersal and ecological drift may generate stochastic patterns. We used pond systems to understand how deterministic and stochastic factors interact and influence tadpole assemblages at different spatial scales. We used variation partitioning and a co-occurrence analysis to evaluate how local environment heterogeneity, species interaction, and spatial variables affected species composition at local and regional scales in Brazilian savanna. Both deterministic and stochastic processes were important to explain tadpole distribution at regional scale, but with a greater contribution of stochastic factors. At local scales, environmental and niche traits were more important to explain tadpole distribution into the habitats. We demonstrate that in Brazilian Cerrado, species composition can be explained by the 'MacArthur paradox,' in which niche processes are important at local scales, whereas dispersal constraints and population processes lead to stochastic patterns in species distribution at large spatial scales. Key words: Anuran larvae, environmental heterogeneity, co-occurrence, geographical scale, community ecology, 1. Introduction Multiple factors and processes can influence the distribution patterns of biological communities (Leibold and Chase 2018), such as historical events, interspecific interactions (Elton 1927; MacArthur and Levins 1967), [...]

One-dimensional Ito stochastic differential equations and stochastic differential equations with local time that depend on a small parameter e and have irregular coefficients (for example, the unlimited drift coefficient or the non-Lipschitz diffusion coefficient) have been considered. The available results concerning the conditions for a mutually univocal correspondence between stochastic Ito equations and stochastic equations with local time were generalized. The weak convergence of the solutions of those equations at [epsilon] [right arrow] 0 were analyzed. The form of the coefficients for the limiting process was obtained. The necessary and sufficient conditions for the weak convergence of the solutions of those equations to the limit random process were proved. Keywords. Ito stochastic differential equations; local time; measures generated by random processes; weak convergence of measures., Introduction It is well known in the theory of stochastic differential equations that the convergence of coefficients is insufficient for the weak convergence of the solutions of Ito stochastic differential [...]

In this paper, we obtain a stochastic criterion for the k-motion of a regular two-dimensional surface in three-dimensional Euclidean space--a stochastic analog of the main theorem of bending theory . Keywords and phrases: surface bending, stochastic process. AMS Subject Classification: 31A10, 60J60 Dedicated to the 80th Anniversary of Professor V. T. Fomenko, In this paper, we obtain a stochastic criterion for the k-motion of a regular surface of nonzero mean curvature and constant-sign Gaussian curvature in three-dimensional Euclidean space. This paper continues [...]

Anyone who has watched an episode of CSI is aware of the value of forensic science--and particularly the impact of DNA, considered the gold standard of the forensic disciplines--on developing [...]

Probabilistic realism and syntactical positivism were two among outdated theories that Feigl criticised on account of their semantical poverty. In this paper, I argue that a refined version of probabilistic realism, which relies on what Feigl specified as the pragmatic description of the symbolic behaviour of scientists' estimations and foresight, is defendable. This version of statistical realism does not need to make the plausibility of realist thesis dependent on the conventional acceptance of a constructed semantic metalanguage. I shall rely on the Prediction Error Minimisation theory (PEM) to support my probabilistic version of realism with a scientifically-informed and naturalistically plausible statistical account of the theories-world relationship which has a pragmatic ring to it., Author(s): Majid Davoody Beni [sup.1] Author Affiliations: (1) grid.411368.9, 0000 0004 0611 6995, Philosophy of Science Group, Department of Management, Science and Technology, Amirkabir University of Technology, , PO Box [...]

We study triage decisions in emergency departments (EDs) and provide a general procedure for determining when to apply provider triage (PT) based on operational and financial considerations using a steady-state, many-server fluid approximation. We then apply the proposed method in the setting of a teaching hospital's ED and obtain closed-form expressions for the range of arrival rates for which PT outperforms the traditional nurse triage economically. We show that the proposed solution methodology based on this approximation procedure is asymptotically optimal under a many-server asymptotic regime. We also demonstrate via simulation experiments that the proposed policy performs within 0.82% of the best solution obtained via a computationally intensive total enumeration method. History: Accepted by Noah Gans, stochastic models and simulation. Funding: T. Tezcan and O. Yildiz were partially supported by the National Science Foundation [Grants CMMI-0954126 and CMMI-1130346]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/mnsc.2017.2982. Keywords: healthcare * hospitals * probability * stochastic model applications * queues * approximations, 1. Introduction Emergency department (ED) crowding has become a significant obstacle to providing timely emergency care in the United States in the last decade as a result of steadily increasing [...]

The first drops of a spring shower splash on a tiled floor in a random fashion, even though they all come from the same rain cloud. In contrast, when a [...]

Abstract. Internet recommender systems are popular in contexts that include heterogeneous consumers and numerous products. In such contexts, product features that adequately describe all the products are often not readily [...]

Abstract. This work presents a steady-state genetic algorithm enhanced by a complete trie-based solution archive for solving the generalized vehicle routing problem with stochastic demands using a preventive restocking strategy. [...]

Abstract. Different solution methods are developed to solve an inventory routing problem for a perishable product with stochastic demands. The solution methods are empirically compared in terms of average profit, [...]

Abstract. In this paper we propose a new estimator for calculating the probability of traffic breakdown as a function of traffic demand. Traffic breakdown is a well-studied phenomena within previous [...]

Abstract. Electric power generation expansion planning (GEP) is the problem of determining an optimal construction and generation plan of both new and existing electric power plants to meet future electricity [...]

OPEC claims to hold and use spare production capacity to stabilize the crude oil market. We study the impact of that buffer on the volatility of oil prices. After estimating the stochastic process that generates shocks to demand and supply, and assessing OPEC's limited ability to accurately measure and offset those shocks, we find that OPEC's use of spare capacity has reduced price volatility, perhaps by as much as half. We also apply the principle of revealed preference to infer the implicit loss function that rationalizes OPEC's investment in spare capacity and compare it to other estimates of the cost of crude oil supply shortfalls. That comparison suggests that OPEC's buffer capacity was in line with global macro-economic needs. Keywords: oil, price volatility, spare capacity, OPEC, revealed preference, 1. INTRODUCTION Spare production capacity plays a central role in the world oil market, and the spare capacity held by OPEC members in particular is significant for its potential ability [...]

Abstract. We develop a high-fidelity simulation model of the patient arrival process to an endocrinology clinic by carefully examining appointment and arrival data from that clinic. The data include the [...]

Abstract. This paper evaluates the robustness of a railway network with respect to operational delays. It assumes that trains in the network operate on fixed routes and with reference to [...]

Abstract. Very often, a train passenger must meet a deadline at the destination, for example, to catch a plane or to arrive at an important meeting on time. Train delays [...]

Abstract. This study considers an integrated closed-loop supply chain (CLSC) network design problem under uncertainty with regard to product demand and return quantities. To incorporate uncertainty in decision making, we [...]

We study a simple adaptive model in the framework of an N-player normal form game. The model consists of a repeated game where the players only know their own action [...]

A commonly investigated linear data assimilation problem as a correction of the numerical model output is defined. This problem means that a numerical model state vector is corrected by observations through a system of linear equations. This paper shows that the asymptotic behavior of the characteristics of objective analyses produced by data assimilation under various conditions exists. In particular, the existence of a stationary regime for this problem is demonstrated, and a special case is discussed when the norm of the Kalman gain matrix approaches zero. For this case the limit theorem for the characteristics of the analysis state vector is proved under certain conditions. Another limit theorem asserts that the model variables after assimilation approach a diffusion stochastic process and the parameters of this process are determined. As a corollary, a new method to determine the gain matrix and the confidence intervals for the analysis state is derived. This led to a new approach on how to realize the data assimilation problem. A few numerical experiments are performed to illustrate the usefulness and feasibility of those theorems., 1. Introduction Data assimilation (DA) techniques are crucial for operational oceanography and weather and climate forecasting [7]. The goal of those techniques is to combine the numerical model ocean and/or [...]

In this paper, we analyze how to continuously adjust the speed in a supply chain with stochastic demand. For each unit (e.g., truckload, shipping container) in the chain, one must [...]